Synesthesia integrates sight, sound and touch into one seamless experience. In computer gaming, it is a design choice in which visuals, user input, and sound are all fused together to create a sensory overload. Think of games like Rez or Child Of Eden, where visuals and sounds come together with controller input.
Rez is an amazing game by Tetsuya Mizuguchi
Child of Eden is a phenomenal visual game with beautiful music
You can create synesthesia with a wonderful free website called Patatap. The instructions are very simple: press any key, from A to Z or the space bar, and observe how a sound and its associated abstract shape become a mesmerizing visual show on your screen. Each stroke on the space bar triggers a different color palette which is associated with a unique sound. The visualisations bring to mind the work of the great artist Kandinsky, who felt shapes and colors represented music. For example he felt triangles were loud and aggressive whereas circles were soft and calm. What masterpiece can you make?